The present invention generally relates to pressurizing syringes which are configured to inherently limit the pressure they supply, and methods of assembling such syringes.
In some procedures involving balloon catheters, medical technicians and doctors must carefully monitor both the balloon's effect on the tissue with which the balloon is engaging, as well as the pressure being delivered by the syringe to the balloon. Pressure monitoring during these procedures must be performed in order to avoid harming tissue or damaging the balloon. In these types of applications, for many years, fluid displacement and pressurization syringes equipped with manometers for monitoring delivered pressure have been used to inflate medical balloon catheters, deliver stents and perform discography.
In certain, less critical medical procedures however, catheter balloons need only be expanded to their full pressure and volume capacity, and therapeutic injections simply must not exceed certain pressure limits. For these types of applications, it is possible to use a more simple, limited pressure delivery syringe. Examples of procedures that can be performed with a simple, limited pressure delivery syringe include: Expansion of tear duct passages to treat epiphora, dilation of sinus passages to restore flow, opening eustachian tubes to promote drainage of the inner ear, and injection of stem cells under controlled delivery pressure. For procedures of these types, the added expense of a manometer to monitor pressure is not essential if the delivery pressure can be controlled with a simple and less expensive pressure limiting mechanism.
U.S. Pat. No. 9,101,739 discloses a pressure-limiting syringe primarily for use in the treatment of sinusitis with a balloon catheter. The device disclosed therein relies upon a syringe having a valve body section contained within a separate housing, a spring controlled internal valve spool, an external bypass channel, a bypassing seal gated shutoff port to stop flow, and a bonded on housing (exposed to pressurized operating fluid) that contains the valve body and an axially oriented Luer connector. The device is relatively complex, and includes many parts.